Abstract
Exaggerated sexually-selected traits, occurring more commonly in males,
help individuals to increase reproductive success, but are costly to
produce and maintain. These costs on the one hand may improve population
fitness by intensifying selection against maladapted males, but on the
other hand may increase the risk of extinction under environmental
challenge. However, the impact of sexually selected traits on extinction
risk have not been investigated experimentally. We used replicate
populations of a male-dimorphic mite, Rhizoglyphus robini, to
test if prevalence of an elaborate, sexually-selected weapon affected
the risk of extinction under gradual temperature increase
(20C per generation). As temperature increased,
individual survival decreased, but this effect was much more dramatic in
populations with high weapon prevalence, compared to populations in
which weapon expression was low. Consequently, the former was
significantly more prone to extinction than the latter, with 75% vs 8%
populations going extinct, respectively. Extinctions occurred despite
partial suppression of the weapon expression at increased temperature,
and were not explained by increased male mortality. Our results provide
the first, to our knowledge, experimental evidence demonstrating
dramatic effect of elaborated sexual traits on the risk of extinction
under environmental challenge.